Effect of dietary isopropanol on the performance and milk quality of dairy cows

The objective of this study was to examine the effects of isopropanol alone or in combination with ethanol on performance, metabolism, and milk quality of dairy cows. Eight crossbred Jersey x Holstein cows (527 +/- 98 kg body weight; 152 +/- 44 days in milk) were allocated in two 4 x 4 balanced-Latin squares to receive one of four dietary treatments. Four cows were surgically adapted with rumen cannula. Diets contained 450 g/kg concentrates and 550 g/kg corn silage either added with (DM basis) 15 g/kg isopropanol, 15 g/kg ethanol, 15 g/kg isopropanol + 15 g/ kg ethanol, or water (control). Immediately before feeding, corn silage was sprayed with alcohols, mixed with concentrates, and fed as total mixed rations twice daily. Dry matter intake, total tract digestibility, ruminal fermentation pattern (pH, volatile fatty acids and NH3), urinary purine derivatives, milk yield, solids composition and oxidative capacity were not affected by treatments. However, gamma-glutamyl transferase activity increased (P < 0.01) in blood of cows supplemented with alcohols, indicating that isopropanol and ethanol were absorbed. Moreover, milk concentration of isopropanol and acetone increased (P < 0.01) in cows receiving isopropanol, but not ethanol. Consequently, milk from cows fed corn silage treated with isopropanol tested false-positive at the ethyl alcohol test in raw milk. In conclusion, dietary isopropanol and ethanol did not impair the performance of dairy cows, but isopropanol was imparted to milk and induced false-positive results at the ethyl alcohol test in raw milk.